src/bin/lttng-sessiond/thread-utils.cpp

   1 /*
   2  * Copyright (C) 2011 EfficiOS Inc.
   3  * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   5  *
   6  * SPDX-License-Identifier: GPL-2.0-only
   7  *
   8  */
   9
  10 #include "lttng-sessiond.hpp"
  11 #include "utils.hpp"
  12
  13 #include <common/utils.hpp>
  14
  15 #include <fcntl.h>
  16 #include <pthread.h>
  17
  18 /*
  19  * Quit pipe for the main thread. This is used by signal handlers to start the
  20  * shutdown sequence of the main thread which will tear down the other threads
  21  * in the appropriate order.
  22  */
  23 static int main_quit_pipe[2] = { -1, -1 };
  24
  25 /*
  26  * Init main quit pipe.
  27  *
  28  * Return -1 on error or 0 if all pipes are created.
  29  */
  30 int sessiond_init_main_quit_pipe()
  31 {
  32         int ret, i;
  33
  34         ret = pipe(main_quit_pipe);
  35         if (ret < 0) {
  36                 PERROR("main quit pipe");
  37                 goto error;
  38         }
  39
  40         for (i = 0; i < 2; i++) {
  41                 ret = fcntl(main_quit_pipe[i], F_SETFD, FD_CLOEXEC);
  42                 if (ret < 0) {
  43                         PERROR("fcntl main_quit_pipe");
  44                         goto error;
  45                 }
  46         }
  47
  48 error:
  49         return ret;
  50 }
  51
  52 /*
  53  * Wait for a notification on the main quit pipe (with a timeout).
  54  *
  55  * A timeout value of -1U means no timeout.
  56  *
  57  * Returns 1 if the caller should quit, 0 if the timeout was reached, and
  58  * -1 if an error was encountered.
  59  */
  60 int sessiond_wait_for_main_quit_pipe(int timeout_ms)
  61 {
  62         int ret;
  63         struct lttng_poll_event events;
  64
  65         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
  66         if (ret < 0) {
  67                 PERROR("Failed to initialize poll/epoll set");
  68                 ret = -1;
  69                 goto end;
  70         }
  71         ret = lttng_poll_add(&events, main_quit_pipe[0], LPOLLIN);
  72         if (ret < 0) {
  73                 PERROR("Failed to add file descriptor to poll/epoll set");
  74                 ret = -1;
  75                 goto end_clean_poll;
  76         }
  77         ret = lttng_poll_wait(&events, timeout_ms);
  78         if (ret > 0) {
  79                 /* Should quit. */
  80                 ret = 1;
  81         } else if (ret < 0 && errno != EINTR) {
  82                 /* Unknown error. */
  83                 PERROR("Failed to epoll()/poll() main quit pipe");
  84                 ret = -1;
  85         } else {
  86                 /* Timeout reached. */
  87                 ret = 0;
  88         }
  89 end_clean_poll:
  90         lttng_poll_clean(&events);
  91 end:
  92         return ret;
  93 }
  94
  95 int sessiond_notify_main_quit_pipe()
  96 {
  97         return notify_thread_pipe(main_quit_pipe[1]);
  98 }
  99
 100 void sessiond_close_main_quit_pipe()
 101 {
 102         utils_close_pipe(main_quit_pipe);
 103 }
 104
 105 /*
 106  * Create a poll set with O_CLOEXEC and add the main quit pipe to the set.
 107  */
 108 int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
 109 {
 110         int ret;
 111
 112         LTTNG_ASSERT(events);
 113
 114         ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
 115         if (ret < 0) {
 116                 goto error;
 117         }
 118
 119         /* Add main quit pipe */
 120         ret = lttng_poll_add(events, main_quit_pipe[0], LPOLLIN);
 121         if (ret < 0) {
 122                 goto error;
 123         }
 124
 125         return 0;
 126
 127 error:
 128         return ret;
 129 }